As a conventional pen, a pen has been used, like a fountain pen, which has such a configuration that a writer holds the rear end portion of a pen body in a state in which a spare ink tank is mounted into the pen body from the rear end side, and writes letters and the like on a writing paper with a pen point at the tip end of the pen body. A large number of such pens have been used because of their convenience of being capable of being used as a writing instrument for a long period of time merely by replacing the spare ink tank, one after another.
In the writing instrument using liquid ink in this manner, however, when the temperature of air in the spare ink tank increases in a state in which the amount of ink in the spare ink tank decreases as the writer uses the writing instrument, the air in the spare ink tank expands, thereby increasing the air pressure. Thereupon, there is a possibility that excess ink is pushed out of the spare ink tank to the pen body and falls in drops from the pen point.
When the spare ink tank is housed in a portion gripped by writer, of the pen body, writers body temperature is conducted to the spare ink tank through the pen body, so that the air in the spare ink tank is easily warmed. In such a case, the ink in the spare ink tank is inevitably pushed out excessively by the air expanded by the body temperature.
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a pen which can always supply a proper amount of ink to a pen point even when the temperature in an ink tank is changed. The present invention accomplishes such by using a capillary tube to feed ink from its storage tank to a fiber pen tip. To avoid either soaking the pen tip or having it go dry when conditions overwhelm the capillary flow causing it to flow an undesired amount of ink, a fluid gap is formed between the capillary tube and the tip with a porous stuffing member positioned thereabout to form a temporary storage device that can take up ink excess flow and then provide it to the tip when it is needed. A compressing structure about the stuffing member can be provided to increase its density and lower its porosity about the gap to increase the capillary force in that area.